Harziphilone and fleephilone, two new HIV REV/RRE binding inhibitors produced by Trichoderma harzianum.

During the screening of the natural products for their ability to inhibit the binding of REV (regulation of virion expression) protein to [33P] labeled RRE (REV responsive element) RNA, two novel fungal metabolites, harziphilone and fleephilone, were isolated from the butanol-methanol (1:1) extract of the fermentation broth of Trichoderma harzianum by bioassay guided fractionation. The structures of these two new compounds were established by spectroscopic methods. Harziphilone and fleephilone showed inhibitory activity against the binding of REV-protein to RRE RNA with IC50 values of 2.0 microM and 7.6 microM, respectively. However both compounds did not protect CEM-SS cells from acute HIV infection at concentration levels up to 200 micrograms/ml using an XTT dye reduction assay. In addition, harziphilone demonstrated cytotoxicity at 38 microM against the murine tumor cell line M-109.

Fluorescence polarization studies of the binding of BMS 181176 to DNA.

The DNA binding of BMS 181176, an antitumor antibiotic derivative of rebeccamycin was characterized by DNA unwinding assays, as well as by fluorescence emission and polarization spectroscopic techniques. Unwinding and rewinding of supercoiled DNA was interpreted in terms of intercalation of BMS 181176 into DNA. BMS 181176 shows an enhanced fluorescence emission upon binding to the AT sequence and no enhancement upon binding to the GC sequence. BMS 181176 appears to be a weaker binder to poly(dAdT).poly(dAdT) compared to doxorubicin and ethidium bromide. When bound to DNA, the rotational motion of BMS 181176 is substantially decreased as evident from the increase in fluorescence polarization. BMS 181176 exhibits a range of binding strengths depending on the DNA. This is demonstrated by the Acridine Orange displacement assay using fluorescence polarization.